Hi Ted,

No worries... when new to this stuff it can be a bit confusing. You have done everything correctly for what you want to do... which is:
You don’t want to hear the CP40, You are using it to trigger some sound engine in your computer (running in Logic Pro).
The CP40 will make no sound while Local Control is Off. Literally called “Local Control” because it indicates the CP40 Keyboard locally playing the CP40 Tone Generator. When Off local control is defeated, you are using the CP40 as a Remote Control device.

Your issue is to get the sound of your computer to the speaker system. That require a piece of equipment called an Audio Interface.
This is a device that can take analog signal in, convert it to digital (called A-to-D conversion) send it to your computer for Audio recording. This device will also be responsible for receiving digital audio from the computer and converting it back to analog (D-to-A) so you can plug it into a sound system. You need this second feature... to get the sound of your plug-in synths to the outside world....

The CP40 is communicating with your computer via USB (bi-directionally, In/Out) for MIDI.
MIDI is not audio. No one has ever heard MIDI. MIDI is a series of coded events that represent a musical performance. These messages must be decoded by a device capable of reading this data. It “represents” a musical performance in the same way the perforated holes in a piano roll (old time player piano scrolls) “represent” a musical performance. You need a specific device to decode the messages and turn them back into sound (music). That’s exactly what MIDI data is... it is no more sound (Audio) than a piece of sheet music. So the CP40 triggers a plug-in synth via these coded messages....

You are using coded messages to trigger the synth sounds in Logic Pro. You press middle “C” at a velocity of 96 on MIDI Channel 1, a coded messages is sent “90 3C 60” this message says: Note On, Channel 1... middle “C”.... velocity 96. Meaningless to anything but another MIDI device.

When that message hits Logic Pro, and is routed to a MIDI TRACK. That Track receives this and sends it to whatever plug-in synth you’ve selected to respond... it is this plug-in synth that is generating the Audio (Sound).... you need to get sound out of the computer and to your sound system. It will need to converted to analog signal by your Audio Interface...

What is your Audio Interface?

Since you don’t mention one, we’ll go ahead and assume you didn’t include it because you don’t have one.
Audio Interfaces come in a variety of sizes, shapes, and price points. You may have noticed that computers don’t have any connectivity that musicians typically use... we are not the principal target customer when they build computers.

There are no traditional audio connectors, no traditional MIDI connectors... Music Recording is one of the many things your computer can do, even though it was not specifically designed for this purpose. By adding the right components and with the right adapters, musicians have been bending the mighty computer to our will for more than 35 years now... an entire niche industry of products exist for elegantly getting music into and back out of the computer.

A computer can, of course, playback music. Not a big deal... to playback music you need to be able to handle two channels (a left and a right audio channel) and you just have to stream the data... easy-peasy. For 94% of the population if all a computer did was PLAYBACK that’d be fine.

The weirdos, that unique 6% of us that are Musicians, we make big time demands on the computer. The stuff that comes with a computer (no matter how much money you’ve spent on it) typically can handle *playback* of a stereo file, heck it can even *record* a stereo file... but what it can’t do efficiently is both simultaneously.

This action of both Playback and Record is called an Overdub. This is when you are listening to previously recorded Tracks while adding a new one. We do it all the time as musicians!!
That, my friend, is the reason there is an entire niche industry of products to solve this issue.

When you press the Spacebar on your computer to playback an audio file: you tap it it plays. You hardly even notice the 300 milliseconds between you hitting the bar and the music sounding... civilians (I refer to non-musicians, as “civilians” ) never do.

Now imagine trying to play along with that music but not being able to hear yourself for 300ms.... trust me, YOU CAN’T PLAY! It’s impossible. It’s an eternity, musically speaking.
Enter the niche market of high speed, low latency devices that get that hideous 300ms down to hopefully double or better, single digit milliseconds...

Any delay longer than 30ms is extremely uncomfortable, if not impossible to play...

Audio Interfaces should be looked at from the viewpoint of “how many simultaneous inputs and what types of inputs” would like to have in your setup... they come in all kinds of varieties from 2 channels to full multi-channeled mixing consoles.

Each Audio Interface may have its own Driver. The Driver instructs the computer on how the audio is going to arrive, and how the computer can return audio to it for conversion. Like in a car, there can be only one Audio Driver (no backseat driving allowed). Mac users have the option of “tricking” the computer by building what is called an Aggregate Audio Device... by trading a few milliseconds of processing time, you are able to construct a single audio device from several external sources.

Thanks BM; I had tripped over the audio interface part and ASSumed that the USB obviated that need since I wasn't using MIDI input jacks. Clearly I was wrong! Will investigate further so I can "bend it to my will" as you so eloquently note. I use an iRig for my bass, so it's not a completely new concept to me (nor latency issues...), just the keyboard side of things. I had a nagging feeling that it was a simple answer.

Appreciate the thorough response; open to any suggestions on Audio Interface recos you may have.

All the best,

Ted

Again it depends on how many things you want to plug in at once and what type of things (for example, do you ever envision recording a microphone?) This is important because depending on the type of microphone you may need your audio interface to provide +48V phantom power (condenser mics)... if you envision recording with a couple of friends or even one other musician you might want to plan ahead.

Plan on recording your keyboard in stereo, so there’s two inputs as a minimum. If you want to play and sing simultaneously you’ll need a three Input (or more) Audio Interface.

Yamaha and Steinberg make small format, high quality audio Interfaces... see the links below for details.

Quick and easy:
Yamaha AG series usb Audio Interfaces

Serious hobbyist:
Steinberg UR Series Audio Interfaces
Steinberg UR-RT Series Audio Interfaces

Cutting edge:
New Steinberg ARX4

Many thanks!